We have recently extended, in central axons of an invertebrate, our earlier work on association between microtubules and mitochondria in chordate axons. Our report, when completed, will compare statistical and observed incidence of multiple association of microtubules with mitochondria from electron micrographs and computed axon 'models' and present further evidence of physical cross-bridges between these structures from both thin-sectioned and freeze-fractured axoplasm. We propose to investigate further the distribution of physical links between microtubules and membrane-limited components in synaptic regions and the cell body of the neurone. We propose to continue collaborative work that has led to the in vitro self-assembly of myosin and actin filaments derived from mammalian skeletal muscle into ordered bipolar contractile units with further studies on the interactions between muscle proteins. BIBLIOGRAPHIC REFERENCES: Braaten, J.T., Jarlfors, U., Smith, D.S. and Mintz, D.H. (1975) Purification of monolayer cultures of the endocrine pancreas. Tissue & Cell 7, 747-762.